1. Technical Field
Embodiments disclosed herein relate to the field of integrated computational elements (ICEs) for optical measurements of fluid samples. In particular, embodiments disclosed herein relate to the field of variable ICEs and methods of fabricating the same.
2. Description of Related Art
In the field of hydrocarbon exploration and extraction there is often the need to perform measurements of samples to determine their chemical composition and other measureable fluid properties. In many cases, methods and systems to perform optical measurements use a spectrally resolved optical element to analyze a sample light. Filters and other spectrally resolved optical devices in state-of-the-art technology are passive devices. Thus, state of the art spectrally resolved optical devices and components typically require continuous re-calibration procedures to correct for fabrication errors, and also to correct for expected drifts due to environmental wear. Furthermore, changing environmental conditions, particularly as experienced in downhole hydrocarbon wells, such as temperature, pressure, and humidity adversely affect the performance of a passive spectrally resolved optical element. Typically, a spectrally resolved optical element or filter includes a plurality of thin dielectric layers prone to contraction or expansion, according to different environmental conditions. The problem is exacerbated when the number of thin dielectric layers is large, such as 10, 20, 50, or even more layers.
Another drawback of conventional filters and other spectrally resolved optical devices is manufacturing repeatability. Indeed, under the most stringent manufacturing tolerances, variability exists in results that need to be considered. Variability adjustments include manufacturing a separate adjustment element especially designed for a particular unit, or introducing continuous calibration measurement steps in the measurement protocols. These approaches are either costly from the manufacturing point of view, or unnecessarily complicate measurement procedures, imposing a heavy load in computational resources, especially as can be applied in downhole hydrocarbon wells.
What is needed is a variable spectrally resolved device allowing real-time error adjustment and environmental adjustment, and a method for using the same in sample measurements.
Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements.